A new apparatus for the determination of vapor permeability of volatile liquid substances through polymer membranes has been described. The permeability of the vapor is calculated from the measurements of the depression rate of the liquid meniscus in a calibrated capillary tube. The conditions of the measurements by means of the described method are very close to those of the average and practical application of foils. The method is characterized by a simple design of the apparatus, easy handling, and simplicity of the determinations, so it may constitute the basis of vapor permeability determination standards. The results obtained by means of the described method were compared with those derived from the partition cell method.